Methods for marking a bare semiconductor die

ABSTRACT

The present invention provides a method and apparatus for marking a semiconductor wafer or device. The method and apparatus have particular application to wafers or devices which have been subjected to a thinning process, including back grinding in particular. The present method comprises reducing the cross-section of a wafer or device, applying a tape having optical energy-markable properties over a surface or edge of the wafer or device, and exposing the tape to an optical energy source to create an identifiable mark. A method for manufacturing an integrated circuit chip and for identifying a known good die are also disclosed. The apparatus of the present invention comprises a multilevel laser-markable tape for application to a bare semiconductor die. In the apparatus, an adhesive layer of the tape provides a homogenous surface for marking subsequent to exposure to electromagnetic radiation.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of application Ser. No.10/092,188, filed Mar. 6, 2002, now U.S. Pat. No. 6,692,978, issued Feb.17, 2004, which application is a divisional of application Ser. No.09/645,904, filed Aug. 25, 2000, now U.S. Pat. No. 6,524,881, issuedFeb. 25, 2003.

BACKGROUND OF THE INVENTION Field of the Invention

[0002] This invention relates generally to marking techniques forsemiconductor wafers and devices. More specifically, the presentinvention relates to methods and apparatus using laser and other opticalenergy-reactive materials for marking the surface of a baresemiconductor die.

[0003] An individual integrated circuit semiconductor die or chip isusually formed from a larger structure known as a semiconductor wafer,which is typically comprised primarily of silicon, although othermaterials such as gallium arsenide and indium phosphide are alsosometimes used. Each semiconductor wafer has a plurality of integratedcircuits arranged in rows and columns with the periphery of eachintegrated circuit being substantially rectangular. In response to theever-increasing demand for smaller, higher performance semiconductordice, wafers are typically thinned (i.e., have their cross-sectionsreduced) by a mechanical and/or chemical grinding process. Afterthinning, the wafer is sawn or “diced” into rectangularly shapeddiscrete integrated circuits along two mutually perpendicular sets ofparallel lines (streets) lying between each of the rows and columnsthereof on the wafer. Hence, the separated or singulated integratedcircuits are commonly referred to as semiconductor die or semiconductordice. While semiconductor dice may carry information of the activesurface thereof regarding the manufacturer, specifications, etc., suchinformation cannot be easily read without the use of optical devices.Subsequent to the wafer-dicing process, individual semiconductor diceare commonly subjected to a marking process wherein various easily readinformation is placed on the back side or inactive side of thesemiconductor die for purposes of corporate identity, productdifferentiation and counterfeit protection.

[0004] Recently, lasers have supplanted the ink stamping process as thequickest and most efficient way to mark finished bare semiconductor diceor packaged semiconductor dice. Thus, lasers are currently used to marksemiconductor dice with a manufacturer's logo, as well as alphanumericmarks and bar codes specifying the company's name, a part or serialnumber, or other information such as lot or die location. In particular,lasers have become especially useful in marking high-production itemssuch as bare or packaged semiconductor dice. The high speed andprecision of laser marking makes their use highly desirable forhigh-throughput automated processes.

[0005] Conventional laser marking techniques utilize a veryhigh-intensity beam of light to alter the surface of a semiconductor diedirectly by melting, burning, or ablating the device surface directly,or by discoloration or decoloration of a laser-reactive coating appliedto a surface of the bare semiconductor die or packaged semiconductordie. The beam of light may be scanned over the surface of the baresemiconductor die or packaged semiconductor die in the requisitepattern, or can be directed through a mask which projects the desiredinscriptions onto the desired surface of the bare semiconductor die orpackaged semiconductor die. The surface or coating of the bare orpackaged semiconductor die thus modified, the laser marking creates areflectivity different from the rest of the surface of the bare orpackaged semiconductor die.

[0006] Numerous methods for laser marking are known in the art. Onemethod of laser marking involves applications where a laser beam isdirected to contact the surface of a semiconductor device directly, asis illustrated in U.S. Pat. Nos. 5,357,077 to Tsuruta, 5,329,090 toWoelki et al., 4,945,204 to Nakamura et al., 4,638,144 to Latta, Jr.,4,585,931 to Duncan et al., and 4,375,025 to Carlson. In these directmarking applications, the roughness of the laser-marked surface isdifferent from that of the unmarked surface. Thus, the contrastgenerated by this type of laser marking is the result of severalfactors, including surface depressions and asymmetry in surface lines.The inscriptions created by burning the surface of the semiconductor diecan therefore be read by holding the device at an angle to a lightsource. An additional factor that may affect the contrast is theremnants of any burnt compounds generated by the laser marking whichhave a different reflectivity from the original material.

[0007] Another method of laser marking makes use of various surfacecoatings, e.g., carbon black and zinc borate, of a different color thanthe underlying device material. When the laser heats the coating to thepoint of vaporization, a readable mark is created by virtue of thecontrast in the two layers. An example of this type of marking methodwas described in U.S. Pat. No. 4,707,722 to Folk et al. The methodsdisclosed by Folk involve the deposition of an ablative coating made ofelectroless nickel layer, in a form highly absorptive of radiant energy,on a surface of a metal package. The ablative coating is then vaporizedby a laser, allowing the shiny metal of the package to show through inthe form of a mark.

[0008] A further method used in the marking of a chip uses materialsknown in the art to be capable of changing color when contacted by alaser beam. For example, U.S. Pat. No. 5,985,377 to Corbett, assigned tothe assignee of the present invention, describes a laser-reactivematerial, such as a material containing a B-stage epoxy with an addedpigment of a desired color, that reacts with heat to form a new compoundon the surface of the chip and subsequently cures to a desired color.Corbett additionally discloses use of an ink-bearing material, such as aribbon, which transfers ink to the surface of a chip when exposed to alaser. U.S. Pat. No. 4,861,620 to Azuma discloses a laser-reactivecoating formed of various pigments, incorporating mercury and otherheavy metals, which will thermally decompose, and hence change colors,when heated to a predetermined temperature by a laser beam. The resultis a mark having a different color from the background color of the chippackage.

[0009] U.S. Pat. No. 4,753,863 to Spanjer describes a laser-markablemolding compound incorporating titanium oxide and/or chromium oxide as acoloring material, polyimide, epoxy, or silicone as a plastic resin, anda filler made of silicon oxide or aluminum oxide. When exposed to alaser, the originally grey molding composition turns a bright goldcolor. U.S. Pat. No. 5,928,842 to Shinmoto et al. discloses a siliconand polyolefin resin-based marking composition which a laser will turnfrom dark brown to black.

[0010] Each of these marking methods, however, is subject to a number ofdrawbacks and limitations. In methods involving the laser marking of abare die, the ideal result is that the burned portion of the surface ofthe semiconductor die becomes sufficiently roughened to become visiblydistinguishable from the semiconductor die's intact smooth surface.However, the laser mark is not always easily recognizable due toinsufficient contrast between the roughened and smooth surfaces. This isparticularly the case with semiconductor dice that have been subjectedto back grinding as part of a wafer thinning process.

[0011] As a result of wafer thinning, the grinding wheel used to abradesilicon from the back side of a wafer having a plurality of locations ofsemiconductor dice formed thereon tends to create swirling patterns onthe back side surface of the wafer and portions of swirling patterns onthe back side surface of the semiconductor dice. These swirling patternsor portions thereof may be sufficiently rough to interfere with anablative laser process, making it much more difficult to burn adistinguishing mark on the surface of the semiconductor die. As afurther result of the operation of the grinding wheel, the pattern leftby the grinding process varies for semiconductor dice taken from oneside of the wafer as opposed to the other, thus adding to the difficultyof reading the mark. An additional problem with bare die laser markingis that the high intensity of the laser beam may cause thermaldegradation of the bare or packaged semiconductor die, or even damagethe internal circuitry of the semiconductor die directly.

[0012] Secondly, use of laser-reactive coatings may not be advantageousfor use in a high-throughput process since many of them take hours tocure. Moreover, many laser coatings will lose the desired degree ofcontrast when exposed to the elevated temperatures prevalent insemiconductor die burn-in tests. Further considerations may weighagainst coatings that incorporate unsafe heavy metals, as well ascoatings that add alpha particle or mobile ion sources known to causedegradation of semiconductor dice. Finally, many coatings are difficultand expensive to apply as they require the use of special apparatusand/or costly materials.

[0013] Accordingly, there exists a need for an inexpensive, quick,high-resolution, and high-quality mark that is compatible with existingsemiconductor fabrication and testing processes. Two of several phasesof the fabrication process that lend themselves to the introduction of acomplementary technique for preparing semiconductor dice for lasermarking are the back grinding and dicing processes.

[0014] During conventional back surface-grinding treatments, asemiconductor wafer is thinned to a desired thickness by the mechanicalaction of a grinding wheel. In processing the semiconductor wafer, thecircuit pattern-formed surface (the “active surface”) of the wafer isprevented from being stained or injured with grinding trashes, etc., bya protective member or submount previously adhered to the circuitpattern-formed surface of the wafer via an automatic adhering apparatus.After applying the back surface grinding treatment, the protectivemember may remain or may be peeled off or dislodged, and thesemiconductor wafer is sent to a subsequent dicing process. To supportand transport the wafer for dicing, a carrier tape or film is typicallyapplied to the back surface of the wafer. Following dicing, thesemiconductor dice are marked with identifying information, and eitherstored, transported, or mounted on carrier substrates such as leadframesor circuit boards which will be populated with an individualsemiconductor die or semiconductor dice. The carrier tape or filmapplied prior to dicing is typically removed during the pick-and-placeprocess of attaching singulated dice to the desired carrier substrate.

BRIEF SUMMARY OF THE INVENTION

[0015] The present invention provides a method and apparatus for markinga semiconductor wafer or semiconductor die. The method and apparatushave particular application to wafers or semiconductor dice which havebeen subjected to a thinning process, including back grinding inparticular. The present method comprises reducing the cross-section of awafer or semiconductor die, applying a tape having opticalenergy-markable properties over a surface or edge of the wafer orsemiconductor die, and exposing the tape to an optical energy source tocreate an identifiable mark. In one embodiment, a markable tape of thepresent invention is applied to a surface which has been roughened byexposure to an abrasive thinning process. The application of the tapecreates a homogenous surface suitable for the formation of an opticalenergy-induced mark, such as that formed by a laser, the mark renderedreadable by virtue of the contrast provided by the tape. In a relatedembodiment, an adhesive affixed to a tape provides the markableproperties of the tape. All, part, or only a residue of the tape mayremain on the wafer or semiconductor die after the marking process. Inthis regard, the tape or a markable adhesive affixed thereon may beadvantageously formed of thermally dissipating and/or antistatic typesof materials. The tape additionally may have a coefficient of thermalexpansion similar to, or the same as, the materials in the wafer or thedevice to which it is applied. Carrier tapes are also disclosed forcomplementary use in the present method wherein the tapes may be formedto have translucent properties, or to provide additional markingqualities.

[0016] In another embodiment, the markable tape is used in a method ofmanufacturing an integrated circuit semiconductor die. This methodbasically entails providing a semiconductor wafer, reducing thecross-section of the semiconductor wafer (for example, by backgrinding), applying the markable tape, dicing the wafer, and subjectingthe diced wafer or individual die to an optical energy source to rendera mark.

[0017] The invention further provides a method for identifying a knowngood die (KGD). In this method, various identifying test data arecompiled and incorporated into an optical energy-generated mark which isformed after the application of a markable tape.

[0018] The invention also includes a laser-markable tape apparatus foruse in marking bare semiconductor dice. The apparatus comprises a tapewhich makes use of a multilevel adhesive that includes an outermostlayer formed of a mixture of electromagnetic radiation-curing componentsand adhesive. After application to a bare semiconductor die and exposureto an electromagnetic radiation source, the mixture layer cures andbonds to the die surface, rendering a homogenous surface suitable forlaser marking.

[0019] Other features and advantages of the present invention willbecome apparent to those of skill in the art through a consideration ofthe ensuing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1A illustrates a top view of a semiconductor wafer that hasbeen thinned through use of a back grinding wheel and subsequentlydiced;

[0021]FIG. 1B depicts a side view of a semiconductor wafer wherein athickness of the wafer has been ground away through a thinning process;

[0022]FIG. 2 illustrates a conventional back grinding apparatus with asemiconductor wafer mounted thereon;

[0023]FIG. 3 shows a simplified schematic view of a conventional lasermarking system capable of readily marking a semiconductor die to whichan optical energy-markable tape has been applied;

[0024]FIG. 4A shows an optical energy-markable tape and a carrier tapeapplied to a back side surface of a thinned semiconductor wafer;

[0025]FIG. 4B illustrates a laser marking tape adhered to a back sidesurface of an individual semiconductor die with the carrier taperemoved;

[0026]FIG. 5 shows multiple layers of laser-markable tape and a carriertape adhered to a back side surface of a thinned semiconductor wafer;and

[0027]FIG. 6 shows a laser-markable tape and a carrier tape separated byan intermediary separating tape.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Referring to drawing FIG. 1A, illustrated is a semiconductorwafer 10 that has been subjected to a thinning process by abrasiveapplication of a back grinding wheel 52 (shown in FIG. 2), and thendiced. Illustrated in drawing FIG. 1B, a side view of wafer 10 is shownwherein a thickness 15 of wafer 10 has been ground away (i.e., across-section has been reduced). Individual semiconductor dice 20 areshown of a type typical to which the laser marking process of thepresent invention is particularly applicable. Semiconductor dice 20 areconfigured with opposing major surfaces, active surface 23 having bondpads located thereon and back side surface 24. In a conventional backgrinding process, a back grinding wheel 52 (drawing FIG. 2) withgrinding surface 53 grinds away semiconductor material from the backside surface 24 of semiconductor die 20 such that grooves or swirlsremain on the back side surface 24 of fully thinned semiconductor die 20(FIG. 1A).

[0029] As shown by the arrows in drawing FIG. 2, back grinding wheel 52of back grinding apparatus 50 typically rotates in one direction 54while a platen 56 providing physical support for semiconductor wafer 10rotates in another direction 58. This results in a grinding pattern thattends to vary from one side of semiconductor wafer 10 as opposed to theother (see drawing FIG. 1A). A submount 17, formed of tape, wax, moldingcompound etc., typically provides protection for the active surface 23of the unsingulated semiconductor die 20 formed on semiconductor wafer10 as well as structural support during the thinning process.

[0030] As can be seen in drawing FIG. 1A, after semiconductor wafer 10has been diced, a semiconductor die 20A from the left side of the wafermay have grind marks 54A going from the upper right to lower left of itsback side surface 24, while a semiconductor die 20B on the right side ofthe wafer may have grind marks 54B which extend from the semiconductordie's upper left to lower right. When bare semiconductor dice 20A and20B are subsequently inscribed by a laser, two factors thus contributeto the difficulty of burning and optically reading a subsequentlyinscribed laser mark on a semiconductor die: the roughness due to thegrooves created on the back side surface 24 of the semiconductor dice,and the differing groove patterns 54A and 54B for each wafer side whichare created by the back grinding process.

[0031] The various embodiments of the present invention providesolutions to the foregoing problem by covering grinding marks on a backside surface 12 of semiconductor wafer 10 with a flexible laser-markabletape 1 (FIG. 3), or a material, dye or residue derived therefrom, thusproviding a substantially smooth and homogenous surface to which a lasermark can be applied and easily read. As used herein, the term “thinningprocess” is used to describe any of the various processes by whichsemiconductor wafers or integrated circuit dice have theircross-sections reduced. In a most preferred embodiment of the presentmethod, thinning occurs by an abrasive back grinding process aspreviously discussed. It is understood, however, that the variousembodiments of the present invention apply to semiconductor dice whichhave been thinned by other processes as well, such as chemicalmechanical polishing, as one example.

[0032] Most basically, the method of the present invention involves thefollowing steps: reducing a cross-section of a semiconductor device;applying a tape having optical energy-markable properties to at least aportion of a surface of the semiconductor device; and exposing at leasta portion of the tape with optical energy to render a mark. This, andother embodiments, including variations thereof, are described in detailbelow.

[0033] Referring now to drawing FIG. 3, shown is a simplified schematicview of a conventional laser marking system 100 capable of readilymarking semiconductor die 20 to which a laser-markable tape 1 has beenapplied. The system comprises a laser 102, a lens system 104, a shadowmask 106, and a laser control system 108 for monitoring and controllingthe function of the apparatus. For purposes of this invention, a “laser”is considered to be any optical energy source capable of marking asurface of a tape or a surface of a semiconductor die or wafer throughthe use of light energy and/or heat. Preferably, laser 102 is comprisedof an Nd:YAG (yttrium aluminum garnet) laser, Nd:YLP (pulsed ytterbiumfiber) laser, carbon dioxide laser, or other suitable optical energydevices known in the art. It is understood, however, that laser 102 mayalso comprise an ultraviolet (UV) energy source or other energy beam.When laser 102 is energized, an intense beam of light 115 is projectedfrom lens system 104 through shadow mask 106 onto front surface 1A oflaser-markable tape 1, laser-markable tape 1 having been placed on theback side surface 24 of thinned semiconductor die 20. When, e.g., alaser beam or intense beam of light 115 impinges on laser-markable tape1, the material of, on, embedded in, attached to, or underlaser-markable tape 1 is altered, e.g., by heating, vaporization,burning, melting, chemical reaction, residue or dye transfer, orcombinations thereof. The result comprises a color or texture change orboth, having the image of shadow mask 106, appearing on the back sidesurface 24 of thinned semiconductor die 20. Although a shadow mask 106is shown in this embodiment, the present invention also contemplatescomputer-directed operation, including mechanical movement, of laser 102in conjunction with, or without, shadow box 106.

[0034] With reference to drawing FIG. 4A, a first embodiment of theinvention is shown wherein laser-markable tape 1, also referred to as“marking tape 1,” is applied to a back side surface 12 of semiconductorwafer 10 after it has been thinned through a back grinding process, anexample of which was depicted in drawing FIG. 2. Semiconductor wafer 10is shown with its front side 11 up, front side 11 containing the circuitpattern-formed surface of the semiconductor wafer 10. A carrier ordicing tape 4 is shown as a second layer disposed over marking tape 1for providing extra stability and support during the dicing ofsemiconductor wafer 10. In drawing FIG. 4B, marking tape 1 is shownadhered to back side surface 24 of individual semiconductor die 20 withcarrier tape 4 removed.

[0035] Marking tape 1 is contemplated for use with a wide variety ofsemiconductor materials and may be applied in any manner known in theart, including, but not limited to, applying the tape by automated ormanual processes, including pick and place or stamping apparatus;applying the tape after it has been precut to the shape of a wafer orportions thereof; applying the tape in narrow or wide strips orswatches; applying the tape as a micro-markable surface; applying thetape to a surface of a wafer after the wafer has been diced; applyingthe tape to all or selected portions of the back side of a wafer or die;applying the tape to a surface of any of the various semiconductor diceknown in the art, such as DIP, SIP, ZIP, PLCC, SOJ, SIMM, DIMM, LCC,QFP, SOP, TSOP, flip-chip, etc; applying the tape in a multilayer formcomprising a combination of one or more other marking tape layers,separation layers, and/or carrier tape layers, etc. Marking tape 1 maythus be applied to a surface on the back side surface 24 of singulatedand separated semiconductor dice. For singulated and separatedsemiconductor dice 20, marking tape 1 may also be applied to one or moreedge surfaces 25 on the semiconductor dice, or to one or more edgesurfaces 25 in combination with a back side surface 24 of semiconductordie 20 in one or several strips. Preferably, marking tape 1 is appliedby an automated process such that marking tape 1 is applied in a highlyregular and standard pattern corresponding to placement onpredetermined, specific areas on singulated semiconductor dice 20, or onwafer areas which will correspond to individual semiconductor dice aftersingulation. As such, vision systems for reading marks on semiconductordice can be adjusted to scan the desired marked areas.

[0036] Use of the terms “laser-markable tape” and “marking tape” areintended to refer to any tape configured such that, upon impact orheating by a laser, component or inherent characteristics of the tapeallow for the formation or transfer of a distinct and permanent orsemipermanent mark onto a surface of a semiconductor die. Examplesinclude, but are not limited to, marking tapes designed to transferinks, dyes, or paints, including fluorescing materials; marking tapeswhich comprise materials which will chemically react with a surface ofthe semiconductor die or another provided material to form a newcompound (as the desired mark) of a contrasting color; marking tapeswhich will transfer a laser-markable residue-type coating or adhesiveonto a semiconductor die; marking tapes which have been “premarked” suchthat exposure to an energy source will reveal the mark; marking tapeswith adhesives that serve as markable materials; and marking tapescomprising materials, textures, and/or colors which contrast with eachother or that of a surface of the semiconductor die and which willvaporize upon laser impact to allow an underlying tape or asemiconductor die color to show through.

[0037] Preferably, the laser marking tape used in the method of thepresent invention will comprise materials which are resistant toblistering, bubbling, or release of volatile components when contactedwith an energy source. One such tape material which is suitable for usein an ablative laser marking process is comprised ofpolytetrafluoroethylene (PTFE), a material which may be made coloredwith various pigments, and which is suitably resistant to blistering,bubbling, or release of volatile components when contacted with a laserbeam.

[0038] By use of the phrase “forming a mark,” the present methodcontemplates the formation of any of a variety of types of marks, aswell as a plurality, or sequence, of identifying marks or characters.Thus, a mark formed or rendered by the present invention may constitute,for example, a corporate logo, a string of alphanumeric characters, abar code, or a binary sequence. Therefore, a “mark,” for purposes of thepresent invention, is in the nature of any form of information which maybe subsequently determined or identified by any means known in the art,including visual scan or otherwise.

[0039] Laser-markable tape 1 preferably has an adhesive layer 2 formedon at least one side thereof, allowing laser-markable tape 1 to betemporarily or permanently adhered to a surface on the back side 12 ofsemiconductor wafer 10, the level of adherence dependent upon thetape-laser application. Alternatively, an adhesive may be applieddirectly to a back side surface 12 of the semiconductor wafer 10 byspray, spin-on or deposition processes and the like. Adhesive layer 2may comprise a pressure-sensitive adhesive, radiation-curable adhesive,B-stage epoxy, or any other adhesive variety known in the art withbonding strength and other characteristics consistent with the type oftape used for the purposes of the invention. For example, inapplications where semiconductor die 20 is to be marked by ablation ofone or more layers of marking tape 1 with a laser, an adhesive layerwith permanent adherence to the die surface may be used for whichvarious epoxy resins or other adhesives known in the art will provesuitable. In applications where inks, dyes, or paints embedded within orcoating marking tape 1 are to be transferred to a surface ofsemiconductor die 20, marking tape 1 need only temporarily bond tosemiconductor die 20 until the mark transfer takes place. Thereafter,marking tape 1 can be peeled or otherwise removed from the surface ofsemiconductor die 20. Laser-markable adhesive layers which arecontemplated for use in the present invention include, but are notlimited to, UV acrylics, thiolene, poly-paraxylylene (Paralene),urethanes, silicones, epoxies, and acrylics.

[0040] It is thus contemplated in one embodiment of the invention thatadhesive layer 2 or the tape itself may be UV-sensitive or sensitive toother electromagnetic radiation so that there is a reduction in thestickiness, adhesiveness or the coefficient of friction of marking tape1 when exposed to a predetermined wavelength of UV light orelectromagnetic radiation. Typically, such a UV-sensitive tape can beformed, for example, of various photo-polymerizable monomers andpolymers, photo-initiators, cross-linking agents, and otherphoto-sensitive agents known in the art. Adhesive layer 2 may also bechemically solvable by any number of solvents, thermally impacted, orotherwise short-lived in its adhesive properties.

[0041] In another embodiment of the invention, marking tape 1 and itsadherence properties are strong enough to provide support for thesemiconductor wafer, in whole or in part, during the transportation,dicing, and/or lasering of semiconductor wafer 10. In a related aspectshown in drawing FIG. 5, marking tape 1 can be readily combined with acarrier or dicing tape 4, or with one or more added layers of markingtape 1B, or a combination of both. Carrier tape 4 can be any of avariety of carrier tapes known in the art for providing support andprotection for semiconductor wafer 10 during various phases of thesemiconductor wafer and semiconductor dice fabrication processes. Thedual layer taping embodiment carries additional advantages during thedicing process in that the extra layer of tape allows for deeper andmore complete cuts into the wafer, supplementary UV shielding, and addedstability which can protect the thinned semiconductor wafers orsemiconductor dice against chipping, splintering, fracturing, etc.during the various phases of the semiconductor fabrication process.

[0042] Marking tape 1 and carrier tape 4 can also be separated by anintermediary separating tape 3 (drawing FIG. 6) that, in one embodiment,facilitates placement and/or removal of the carrier tape over markingtape 1. As previously described, it is also contemplated that a singlelayer of marking tape 1 and its adhesive layer 2 be sufficiently strongso as to provide the sole support for semiconductor wafer 10 duringtransportation and dicing.

[0043] In an aspect of the invention wherein marking tape 1 is combinedwith a carrier tape 4, carrier tape 4 may have translucent properties orbe formed at a low density which allows light from a laser to penetratecarrier tape 4 and impact marking tape 1 to effect the mark.

[0044] Carrier tape 4 or an adhesive layer thereof may also be formed tobe relatively weakly adhesive to marking tape 1, or a multilevelvariation thereof, allowing for easy removal of the carrier tape priorto, after, or during the laser marking of semiconductor die 20. In apreferred embodiment, the adhesive layer of the carrier tape is UV- (orelectromagnetic radiation-) sensitive such that upon exposure to UVlight (or electromagnetic radiation), the adhesive properties of carriertape 4 are reduced, and carrier tape 4 may be easily peeled away orremoved from marking tape 1. One such carrier tape and adhesivecombination suitable for purposes of the invention comprises aUV-penetrable polyvinyl chloride tape with an acrylic UV-sensitiveadhesive.

[0045] As previously described, it is further contemplated that markingtape 1 can be applied in a plurality of marking tape layers 1B. Inaddition to providing added support and protection for the wafer, themarking tape layers can be constructed such that one or more tapescontain one or more pigments transferable to the surface of the die.Alternatively, materials comprising multiple layers of marking tape maybe formed to chemically react with one another, and/or a surface of thesemiconductor die, in the presence of a laser to form a discernablemark.

[0046] In a further embodiment involving a plurality of marking tapes,one or more of which may comprise contrasting colors, a first markingtape layer of a color is provided adhesively in contact with a surfaceof a bare semiconductor die. A second marking tape layer of a secondcolor is disposed on the first marking tape layer, the color of which isselected to clearly contrast to that of the first layer. A laser beam isthen controlled in intensity such that the outer second layer is piercedselectively, thus creating a detectable mark corresponding to thecontrasting color of the lower marking tape layer. Three or more layers,preferably each of a different color, could also be utilized with one ormore layers selectively pierced to create a desired mark. Preferably,the outer marking layers are formed to have a lower material densitythan the inner marking layers.

[0047] Preferably, marking tape 1 is formed of a material which has asimilar coefficient of thermal expansion to that of the semiconductordie, and is advantageously made of a thermally dissipating material.Marking tape 1 can also have antistatic capacities for preventing thegeneration of static electricity during the adhering or peeling ofcarrier tape 4. Antistatic properties can be produced in marking tape 1by appropriate methods, including the introduction of antistatic orconductive agents during the formation of marking tape 1.

[0048] In another preferred embodiment, carrier tape 4 can be used inconjunction with one or more levels of adhesives, at least one of theadhesives comprising laser-markable components when disposed on asurface of a bare semiconductor die 20. In one embodiment, a markableadhesive layer 1B (not shown) serves to bind carrier tape 4 to a baresurface on the back side surface 12 of semiconductor wafer 10, and willtransfer a laser-markable residue to a surface of semiconductor die 20when carrier tape 4 is later removed. In this case, carrier tape 4functions to provide a support and protective function duringsemiconductor processing, but can be peeled away to effect transfer ofthe laser-markable residue.

[0049] In a second related example, a carrier tape 4 with a multilayeradhesive can be used wherein a first layer of the multilayer adhesivecomprises a mixture of electromagnetic radiation-curing components andan adhesive. The first mixture layer is formed of a type so as to cureand bond to a surface of a bare semiconductor die 20 upon exposure to aradiation source, whereupon it is laser markable. A second adhesivelayer can be provided over the first mixture layer, the second adhesivelayer providing adherence to both the first mixture layer and carriertape 4. The second adhesive layer may also be formed to beelectromagnetic radiation-curable and adhere to the first mixture layerand carrier tape 4 in an uncured state. Upon exposure to radiation, thesecond adhesive layer can either cure onto the first mixture layer or,alternatively, lose its adhesive properties and facilitate peeling ofcarrier tape 4 from a wafer or surface of a bare semiconductor die 20.

[0050] It is further contemplated that laser-markable tape 1 and theother embodiments of the present invention may also be combined in anadjunct manner to, or as a component of, other laser, thermal, orrelated marking methods, such as use of various coatings, markablecompounds or laser-markable chemicals or films. The embodiments of theinvention are further applicable to the remarking of previously markeddice which, for example, have been mismarked, marked upside down ormarked in a backwards fashion.

[0051] As previously discussed, the method of the present invention iscontemplated for use in rendering a myriad variety of marks, includingmarks for purposes of corporate identity, product differentiation andcounterfeit protection. In a preferred embodiment, the variousapplications of creating a mark through use of marking tape 1 may beused in conjunction with semiconductor wafer or integrated circuitsemiconductor die testing to identify a known good die (KGD). In suchapplications, previously thinned semiconductor wafers or individualintegrated circuit semiconductor dice are subjected to burn-in, visualscans, or other processes known in the art to detect defects. Suchdefect data is then typically stored in a computer or other memory/datacompiling device. Subsequent to receiving the results of such testingprocedures, marking tape 1 is applied and exposed to an energy sourceand encoded with information comprising the results of the defect/knowngood die (KGD) tests. One of skill in the art will recognize that incarrying out this process, marking tape 1 in the various embodimentspreviously described may be applied to a surface of the semiconductorwafer or integrated before or after such defect testing.

[0052] It will be appreciated by those skilled in the art that theembodiments herein described while illustrating certain embodiments arenot intended to so limit the invention or the scope of the appendedclaims. Those skilled in the art will also understand that variouscombinations or modifications of the preferred embodiments could be madewithout departing from the scope of the invention.

[0053] For example, this invention, while being described with referenceto semiconductor wafers containing integrated circuits and individualsemiconductor dice, has equal utility to any type of substrate to beinscribed. The embodiments of the present invention are alsocontemplated for use on semiconductor wafer and semiconductor diesurfaces other than a ground back side surface, and can be applied atany stage in the semiconductor die fabrication process. Accordingly, theinvention can be utilized on the front side, edges, or on an ungroundback surface of a semiconductor wafer or semiconductor die. In addition,the invention may be applied to encapsulated semiconductor die packages.

[0054] Further, the present invention has additional applicability tothe laser marking of custom or nonstandard ICs or other components,wherein a capability for rapid and easy die marking on a semiconductorwafer-by-semiconductor wafer or semiconductor die-by-semiconductor diebasis is highly beneficial and cost-effective.

[0055] Thus, while certain representative embodiments and details havebeen shown for purposes of illustrating the invention, it will beapparent to those skilled in the art that various changes in theinvention disclosed herein may be made without departing from the scopeof the invention, which is defined in the appended claims.

What is claimed is:
 1. A method of marking a packaged semiconductordevice comprising: providing a semiconductor die having a reducedcross-section in wafer form; packaging said semiconductor die forming apackaged semiconductor device, said packaged semiconductor device havinga surface; applying a tape having optical energy-markable properties toat least a portion of said surface of said packaged semiconductordevice; subsequently exposing at least a portion of said tape to opticalenergy; and forming a mark.
 2. The method of claim 1, wherein saidpackaged semiconductor device comprises at least one integrated circuitsemiconductor die.
 3. The method of claim 1, wherein said applying atape to at least a portion of said surface of said packagedsemiconductor device includes applying said tape to an edge portion ofsaid packaged semiconductor device.
 4. The method of claim 3, whereinsaid exposing at least a portion of said tape to optical energy includesexposing said tape on said edge portion of said packaged semiconductordevice.
 5. The method of claim 1, wherein said optical energy-markableproperties of said tape are embedded within said tape.
 6. The method ofclaim 1, wherein said optical energy-markable properties of said tapecomprise properties of at least one adhesive layer affixed to said tape.7. The method of claim 6, wherein said at least one adhesive layer isselected from one of thiolene, poly-paraxylylene (Paralene), urethanes,silicones, epoxies, acrylics, or combinations of any thereof.
 8. Themethod of claim 6, wherein said at least one adhesive layer isUV-sensitive.
 9. The method of claim 6, wherein said at least oneadhesive layer includes a multilayer adhesive having a first outermostlayer comprising a mixture of electromagnetic radiation-curablecomponents and a second layer disposed between said tape and said firstoutermost layer.
 10. The method of claim 1, further comprising: applyinga second tape over at least a portion of a surface of said tape; andexposing at least a portion of said second tape.
 11. The method of claim10, wherein said second tape is a carrier tape.
 12. The method of claim11, wherein said carrier tape includes a carrier tape having translucentproperties.
 13. The method of claim 11, wherein said second tapeincludes a tape having optical energy-markable properties.
 14. Themethod of claim 1, wherein said tape comprises polytetrafluoroethylenetape.
 15. The method of claim 1, wherein said exposing at least aportion of said tape to optical energy comprises exposing said at leasta portion of said tape to one of an Nd:YAG laser (yttrium aluminumgarnet), an Nd:YLP laser (pulsed ytterbium fiber), or carbon dioxidelaser.
 16. The method of claim 1, wherein said exposing at least aportion of said tape to optical energy includes exposing said at least aportion of said tape to an ultraviolet light source.
 17. The method ofclaim 16, wherein said tape is comprised of a UV-penetrable polyvinylchloride tape with an acrylic UV-sensitive adhesive disposed thereon.18. The method of claim 1, wherein said tape includes a tape havingantistatic capacities.
 19. The method of claim 1, wherein said tapeincludes a tape of a thermally dissipating material.
 20. The method ofclaim 1, wherein said tape includes a tape having a coefficient ofthermal expansion substantially similar to that of said packagedsemiconductor device.
 21. The method of claim 1, wherein said formingsaid mark includes one of heating, chemically reacting, or transferringmaterials comprising said tape.
 22. A method of marking a packagedsemiconductor device having a semiconductor die comprising: providingsaid semiconductor die in wafer form; packaging said semiconductor dieforming a packaged semiconductor device, said packaged semiconductordevice having a surface; applying a tape having optical energy-markableproperties to at least a portion of said surface of said packagedsemiconductor device; subsequently exposing at least a portion of saidtape to optical energy; and forming a mark.
 23. The method of claim 22,wherein said packaged semiconductor device comprises at least oneintegrated circuit semiconductor die.
 24. The method of claim 22,wherein said applying a tape to at least a portion of a surface of saidpackaged semiconductor device includes applying said tape to an edgeportion of said packaged semiconductor device.
 25. The method of claim24, wherein said exposing at least a portion of said tape to opticalenergy includes exposing said tape on said edge portion of said packagedsemiconductor device.
 26. The method of claim 22, wherein said opticalenergy-markable properties of said tape are embedded within said tape.27. The method of claim 22, wherein said optical energy-markableproperties of said tape comprise properties of at least one adhesivelayer affixed to said tape.
 28. The method of claim 27, wherein said atleast one adhesive layer is selected from one of thiolene,poly-paraxylylene (Paralene), urethanes, silicones, epoxies, acrylics,or combinations of any thereof.
 29. The method of claim 27, wherein saidat least one adhesive layer is UV-sensitive.
 30. The method of claim 27,wherein said at least one adhesive layer includes a multilayer adhesivehaving a first outermost layer comprising a mixture of electromagneticradiation-curable components and a second layer disposed between saidtape and said first outermost layer.
 31. The method of claim 22, furthercomprising: applying a second tape over at least a portion of a surfaceof said tape; and exposing at least a portion of said second tape. 32.The method of claim 31, wherein said second tape is a carrier tape. 33.The method of claim 32, wherein said carrier tape includes a carriertape having translucent properties.
 34. The method of claim 32, whereinsaid second tape includes a tape having optical energy-markableproperties.
 35. The method of claim 22, wherein said tape comprisespolytetrafluoroethylene tape.
 36. The method of claim 22, wherein saidexposing at least a portion of said tape to optical energy comprisesexposing said at least a portion of said tape to one of an Nd:YAG laser(yttrium aluminum garnet), an Nd:YLP laser (pulsed ytterbium fiber), orcarbon dioxide laser.
 37. The method of claim 22, wherein said exposingat least a portion of said tape to optical energy includes exposing saidat least a portion of said tape to an ultraviolet light source.
 38. Themethod of claim 37, wherein said tape is comprised of a UV-penetrablepolyvinyl chloride tape with an acrylic UV-sensitive adhesive disposedthereon.
 39. The method of claim 22, wherein said tape includes a tapehaving antistatic capacities.
 40. The method of claim 22, wherein saidtape includes a tape of a thermally dissipating material.
 41. The methodof claim 22, wherein said tape includes a tape having a coefficient ofthermal expansion substantially similar to that of said packagedsemiconductor device.
 42. The method of claim 22, wherein said formingsaid mark includes at least one of heating, chemically reacting, ortransferring materials comprising said tape.
 43. A method of marking asemiconductor die comprising: providing a semiconductor die having areduced cross-section in wafer form; packaging said semiconductor dieforming a packaged semiconductor device, said packaged semiconductordevice having a surface; applying a tape having optical energy-markableproperties to at least a portion of said surface of said packagedsemiconductor device; subsequently exposing at least a portion of saidtape to optical energy; and forming a mark.
 44. The method of claim 43,wherein said semiconductor die comprises at least one integrated circuitsemiconductor die.
 45. The method of claim 43, wherein said applying atape to at least a portion of a surface of said semiconductor dieincludes applying said tape to an edge portion of said semiconductordie.
 46. The method of claim 45, wherein said exposing at least aportion of said tape to optical energy includes exposing said tape onsaid edge portion of said semiconductor die.
 47. The method of claim 43,wherein said optical energy-markable properties of said tape areembedded within said tape.
 48. The method of claim 43, wherein saidoptical energy-markable properties of said tape comprise properties ofat least one adhesive layer affixed to said tape.
 49. The method ofclaim 48, wherein said at least one adhesive layer is selected from oneof thiolene, poly-paraxylylene (Paralene), urethanes, silicones,epoxies, acrylics, or combinations of any thereof.
 50. The method ofclaim 48, wherein said at least one adhesive layer is UV-sensitive. 51.The method of claim 48, wherein said at least one adhesive layerincludes a multilayer adhesive having a first outermost layer comprisinga mixture of electromagnetic radiation-curable components and a secondlayer disposed between said tape and said first outermost layer.
 52. Themethod of claim 43, further comprising: applying a second tape over atleast a portion of a surface of said tape; and exposing at least aportion of said second tape.
 53. The method of claim 52, wherein saidsecond tape is a carrier tape.
 54. The method of claim 53, wherein saidcarrier tape includes a carrier tape having translucent properties. 55.The method of claim 53, wherein said second tape includes a tape havingoptical energy-markable properties.
 56. The method of claim 43, whereinsaid tape comprises polytetrafluoroethylene tape.
 57. The method ofclaim 43, wherein said exposing at least a portion of said tape tooptical energy comprises exposing said at least a portion of said tapeto one of an Nd:YAG laser (yttrium aluminum garnet), an Nd:YLP laser(pulsed ytterbium fiber), or carbon dioxide laser.
 58. The method ofclaim 43, wherein said exposing at least a portion of said tape tooptical energy includes exposing said at least a portion of said tape toan ultraviolet light source.
 59. The method of claim 58, wherein saidtape is comprised of a UV-penetrable polyvinyl chloride tape with anacrylic UV-sensitive adhesive disposed thereon.
 60. The method of claim43, wherein said tape includes a tape having antistatic capacities. 61.The method of claim 43, wherein said tape includes a tape of a thermallydissipating material.
 62. The method of claim 43, wherein said tapeincludes a tape having a coefficient of thermal expansion substantiallysimilar to that of said packaged semiconductor device.
 63. The method ofclaim 43, wherein said forming said mark includes one of heating,chemically reacting, or transferring materials comprising said tape. 64.A method of marking a semiconductor die after a thinning process forreducing a thickness of said semiconductor die, said semiconductor diehaving an active surface and a thinned surface, said method comprising:providing said semiconductor die in wafer form; applying a tape havingoptical energy-markable properties to at least a portion of said thinnedsurface of said semiconductor die; subsequently exposing at least aportion of said tape to optical energy; and forming a mark on a portionof said semiconductor die.
 65. The method of claim 64, wherein saidsemiconductor die comprises at least one integrated circuitsemiconductor die.
 66. The method of claim 64, wherein said applying atape to at least a portion of said thinned surface of said semiconductordie includes applying said tape to an edge portion of said semiconductordie.
 67. The method of claim 66, wherein said exposing at least aportion of said tape to optical energy includes exposing said tape onsaid edge portion of said semiconductor die.
 68. The method of claim 64,wherein said optical energy-markable properties of said tape areembedded within said tape.
 69. The method of claim 64, wherein saidoptical energy-markable properties of said tape comprise properties ofat least one adhesive layer affixed to said tape.
 70. The method ofclaim 69, wherein said at least one adhesive layer is selected from oneof thiolene, poly-paraxylylene (Paralene), urethanes, silicones,epoxies, acrylics, or combinations of any thereof.
 71. The method ofclaim 69, wherein said at least one adhesive layer is UV-sensitive. 72.The method of claim 69, wherein said at least one adhesive layerincludes a multilayer adhesive having a first outermost layer comprisinga mixture of electromagnetic radiation-curable components and a secondlayer disposed between said tape and said first outermost layer.
 73. Themethod of claim 64, further comprising: applying a second tape over atleast a portion of a surface of said tape; and exposing at least aportion of said second tape.
 74. The method of claim 73, wherein saidsecond tape is a carrier tape.
 75. The method of claim 74, wherein saidcarrier tape includes a carrier tape having translucent properties. 76.The method of claim 74, wherein said second tape includes a tape havingoptical energy-markable properties.
 77. The method of claim 64, whereinsaid tape comprises polytetrafluoroethylene tape.
 78. The method ofclaim 64, wherein said exposing at least a portion of said tape tooptical energy comprises exposing said at least a portion of said tapeto one of an Nd:YAG laser (yttrium aluminum garnet), an Nd:YLP laser(pulsed ytterbium fiber), or carbon dioxide laser.
 79. The method ofclaim 64, wherein said exposing at least a portion of said tape tooptical energy includes exposing said at least a portion of said tape toan ultraviolet light source.
 80. The method of claim 79, wherein saidtape is comprised of a UV-penetrable polyvinyl chloride tape with anacrylic UV-sensitive adhesive disposed thereon.
 81. The method of claim64, wherein said tape includes a tape having antistatic capacities. 82.The method of claim 64, wherein said tape includes a tape of a thermallydissipating material.
 83. The method of claim 64, wherein said tapeincludes a tape having a coefficient of thermal expansion substantiallysimilar to that of said packaged semiconductor device.
 84. The method ofclaim 64, wherein said forming said mark includes one of heating,chemically reacting, or transferring materials comprising said tape. 85.A method of marking a packaged semiconductor device comprising:providing a semiconductor die having a reduced cross-section in slicedwafer form; packaging said semiconductor die forming a packagedsemiconductor device, said packaged semiconductor device having asurface; applying a tape having optical energy-markable properties to atleast a portion of said surface of said packaged semiconductor device;subsequently exposing at least a portion of said tape to optical energy;and forming a mark.
 86. A method of marking a packaged semiconductordevice having a semiconductor die comprising: providing saidsemiconductor die in sliced wafer form; packaging said semiconductor dieforming a packaged semiconductor device, said packaged semiconductordevice having a surface; applying a tape having optical energy-markableproperties to at least a portion of said surface of said packagedsemiconductor device; subsequently exposing at least a portion of saidtape to optical energy; and forming a mark.
 87. A method of marking asemiconductor die comprising: providing a semiconductor die having areduced cross-section in sliced wafer form; packaging said semiconductordie forming a packaged semiconductor device, said packaged semiconductordevice having a surface; applying a tape having optical energy-markableproperties to at least a portion of said surface of said packagedsemiconductor device; subsequently exposing at least a portion of saidtape to optical energy; and forming a mark.
 88. A method of marking asemiconductor die after a thinning process for reducing a thickness ofsaid semiconductor die, said semiconductor die having an active surfaceand a thinned surface, said method comprising: providing saidsemiconductor die in sliced wafer form; applying a tape having opticalenergy-markable properties to at least a portion of said thinned surfaceof said semiconductor die; subsequently exposing at least a portion ofsaid tape to optical energy; and forming a mark on a portion of saidsemiconductor die.
 89. A method of marking a packaged semiconductordevice comprising: providing a semiconductor die having a reducedcross-section as a portion of a wafer; packaging said semiconductor dieforming a packaged semiconductor device, said packaged semiconductordevice having a surface; applying a tape having optical energy-markableproperties to at least a portion of said surface of said packagedsemiconductor device; subsequently exposing at least a portion of saidtape to optical energy; and forming a mark.
 90. A method of marking apackaged semiconductor device having a semiconductor die comprising:providing said semiconductor die as apportion of a wafer; packaging saidsemiconductor die forming a packaged semiconductor device, said packagedsemiconductor device having a surface; applying a tape having opticalenergy-markable properties to at least a portion of said surface of saidpackaged semiconductor device; subsequently exposing at least a portionof said tape to optical energy; and forming a mark.
 91. A method ofmarking a semiconductor die comprising: providing a semiconductor diehaving a reduced cross-section as a portion of a wafer; packaging saidsemiconductor die forming a packaged semiconductor device, said packagedsemiconductor device having a surface; applying a tape having opticalenergy-markable properties to at least a portion of said surface of saidpackaged semiconductor device; subsequently exposing at least a portionof said tape to optical energy; and forming a mark.
 92. A method ofmarking a semiconductor die after a thinning process for reducing athickness of said semiconductor die, said semiconductor die having anactive surface and a thinned surface, said method comprising: providingsaid semiconductor die as a portion of a wafer; applying a tape havingoptical energy-markable properties to at least a portion of said thinnedsurface of said semiconductor die; subsequently exposing at least aportion of said tape to optical energy; and forming a mark on a portionof said semiconductor die.
 93. A method of marking a packagedsemiconductor device comprising: providing a semiconductor die having areduced cross-section as a portion of a sliced wafer; packaging saidsemiconductor die forming a packaged semiconductor device, said packagedsemiconductor device having a surface; applying a tape having opticalenergy-markable properties to at least a portion of said surface of saidpackaged semiconductor device; subsequently exposing at least a portionof said tape to optical energy; and forming a mark.
 94. A method ofmarking a packaged semiconductor device having a semiconductor diecomprising: providing said semiconductor die as a portion of a slicedwafer; packaging said semiconductor die forming a packaged semiconductordevice, said packaged semiconductor device having a surface; applying atape having optical energy-markable properties to at least a portion ofsaid surface of said packaged semiconductor device; subsequentlyexposing at least a portion of said tape to optical energy; and forminga mark.
 95. A method of marking a semiconductor die comprising:providing a semiconductor die having a reduced cross-section as aportion of a sliced wafer; packaging said semiconductor die forming apackaged semiconductor device, said packaged semiconductor device havinga surface; applying a tape having optical energy-markable properties toat least a portion of said surface of said packaged semiconductordevice; subsequently exposing at least a portion of said tape to opticalenergy; and forming a mark.
 96. A method of marking a semiconductor dieafter a thinning process for reducing a thickness of said semiconductordie, said semiconductor die having an active surface and a thinnedsurface, said method comprising: providing said semiconductor die as aportion of a sliced wafer; applying a tape having opticalenergy-markable properties to at least a portion of said thinned surfaceof said semiconductor die; subsequently exposing at least a portion ofsaid tape to optical energy; and forming a mark on a portion of saidsemiconductor die.